Member Function Wrapper

MemberFuncFunctor.cpp

#include <print>

struct Foo {
    int x;

    Foo() noexcept
    : x {0} {}

    [[nodiscard]] int operator()() noexcept {
        return ++x;
    }
};

template <typename Class, typename Result, typename... Args>
class FunctorStore {
private:
    using member_fn_t = Result(Class::*)(Args...);
    member_fn_t m_fp;

public:
    constexpr FunctorStore() noexcept
    : m_fp {nullptr} {}

    explicit constexpr FunctorStore(member_fn_t fp_) noexcept
    : m_fp {fp_} {}

    template <typename... Args2>
    [[nodiscard]] Result operator()(Class* self, Args2&&... args2) noexcept(noexcept((self->*m_fp)(args2...))) {
        return (self->*m_fp)(args2...);
    }
};

int main() {
    Foo f;

    FunctorStore store_fun {&Foo::operator()};

    std::print("answer = {}\n", store_fun(&f));
}